Ribbon cables often have a series of electrical conductors embedded next to each other in an insulation material. These conductors can be round with a circular cross section and/or flat with a rectangular cross section. Conventional plug-in connector housings have a cable plug-in opening to accept an end portion of a ribbon cable. Conductor contacts, in the form of conductor contact receptacles, electrically contact ribbon cable conductors when the cable is inserted into a plug-in connector housing. The conductor contacts are electrically connected to terminal contacts that can be electrically connected, for example, to the strip conductors of a printed circuit board.
In order to permit electrical contacting between the ribbon cable conductors and conductor contacts of the plug-in connector, the ribbon cable conductors are often exposed on one ribbon cable end, on a broad side of the ribbon cable, by stripping the insulation down to the ribbon cable conductors. However, the ribbon cable end loses its bending rigidity when the insulation on the ribbon cable end is stripped. A loss of rigidity hampers the inserting of the ribbon cable end into the cable plug-in opening of the plug-in connector and complicates problem-free electrical contacting between the exposed ribbon cable conductors and the conductor contacts.
To overcome this shortcoming, in the past a reinforcement layer, preferably in the form of a reinforcement sheet, has been applied on the broad side of the ribbon cable end on which the ribbon cable conductors are not exposed, i.e., no insulation has been removed. This has increased the bending rigidity of the ribbon cable end which was reduced by the stripping of the insulation. A material with a relatively high intrinsic bending rigidity has been used for the reinforcement sheet. Notwithstanding such an attempt to increase the rigidity of the stripped ribbon cable, this design suffers from shortcomings which detract from its usefulness.
A conventional ribbon cable has a sheet structure with a thickness of about 0.4 mm. The plug-in connectors commonly used for the connection of such a ribbon cable have a limited design height of about 10 mm. From the beginning of the cable plug-in opening, to the spring contacts of a conductor contact, a lateral guide for the thin ribbon cable exists only over a short zone of about 7 mm. Additionally, common plug-in connectors for connection of such ribbon cables have significant manufacturing tolerances. This means that the ribbon cable end must be plugged into the cable plug-in opening of the plug-in connector with only limited guide depth and unreliable lateral guiding. The ribbon cable end is likely to be plugged into the plug-in connector obliquely or with kinks. Misalignment of the ribbon cable with respect to the plug-in connector may cause the ribbon cable conductors to not properly contact corresponding conductor contacts.
In particular, such a problem arises in shielding flat conductor ribbon cables that have a shielding sheet situated above a layer of insulation material on each broad side of the cable, and in which a flat conductor situated on a longitudinal edge of the cable is in contact with both shielding sheets. The shielding sheets lie on this flat conductor without interposition of insulation material. Since insulation is lacking in this longitudinal edge region of the flat conductor ribbon cable, this longitudinal edge region is particularly labile.
The force with which the contact spring arms of the conductor contacts engage the ribbon cable conductors is limited given the very small size of the conductor contacts. Therefore, the ribbon cable conductors may loosen from the conductor contacts even if a small tensile force is exerted on the ribbon cable. However, such loosening is not acceptable in applications which demand a particularly high reliability of the plug-in connection between the ribbon cable end and the plug-in connector.
Additionally, ribbon cables often have an electrical shield in the form of a shielding sheet situated between an insulation material surrounding the ribbon cable conductors and an insulation material sheath of the ribbon cable. This shielding sheet needs to be electrically grounded. One way of providing this ground is by using an additional wire to connect the ribbon cable shield to either the plug-in connector shield or the ground conductor of a printed circuit board. Shielding quality, as is desired in high-grade applications, is not possible with this design.
The foregoing illustrates limitations known to exist in present plug-in connectors for ribbon cables. Thus, it is apparent that it would be advantageous to provide an improved plug-in connector directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.